I haven't watched the serial in a while to remember if we really see a Kroton standing directly right next to a person on the same flat surface.

I think that the Doctor and Zoe are in a small platform with that control console thingy...

Even so...Eaglemoss has up to this point done an excellent job in making these accurate, so I trust that maybe they actually were this tall? After all...there's no head in the "head" as that part of the costume rotated, so the person inside had to be fully inside the "body" part. Additionally, the figurine base on the Kroton is taller than that of the Doctor, and Patrick and Wendy were kind of short anyway.